title: Inhibition of ADH-stimulated water flow by stable prostaglandin endoperoxide analogues.
abstract: The synthetic prostaglandin endoperoxide analogues 15-hydroxy-9,11-(epoxymethano)prosta-5,13-dien-1-oic acid (EPA-I) and 15-hydroxy-11,9-(epoxymethano)prosta-5,13-dien-1-oic acid (EPA-II) inhibited ADH-induced water flow in the isolated urinary bladder of the toad. In certain other biologic systems, EPA-I appeared to possess "thromboxane-like" activity. Thromboxanes, therefore, as well  as the classical E prostaglandins may be modulators of the ADH response. To further characterize the effect of EPA-I on ADH, interaction studies were conducted with a related endoperoxide analogue found to be devoid of anti-ADH activity, 9,11-(epoxymethano)prostan-1-oic acid (EPA-III), and a prostanoid found to be a PGE antagonist in isolated toad bladder, 7-oxa-13-prostynoic acid. EPA-III reversed the anti-ADH activity of EPA-I but not that of PGE2. In contrast, 7-oxa-13-prostynoic acid reversed the anti-ADH activity of PGE2 but not that of an equieffective concentration of EPA-I. These findings suggest that the anti-ADH activity of EPA-I, and by inference thromboxane A2, may be mediated via a different receptor and/or pathway than that of the E prostaglandins.
mesh_terms: D000818:Animals; D001692:Biological Transport; D002024:Bufo marinus / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D066298:In Vitro Techniques; D011450:Prostaglandin Endoperoxides, Synthetic / Q000494:pharmacology*; D001743:Urinary Bladder / Q000378:metabolism*; D014667:Vasopressins / Q000037:antagonists & inhibitors / Q000494:pharmacology; D014867:Water / Q000378:metabolism*
chemical_list: D011450:Prostaglandin Endoperoxides, Synthetic; D014867:Water; D014667:Vasopressins